Introduction: To investigate the relation of circulating levels of leptin with cognition in Alzheimer's disease (AD) patients.

Methods: Thirty patients meeting the clinical diagnostic criteria for AD and twenty-five healthy controls were enrolled into the study. At baseline, all patients underwent standing height, weight measurements and waist circumference (in centimeters) using a standard scale. Body mass index (BMI) was then calculated as weight (in kilograms). A single 5-ml fasting blood sample was obtained from each patient. All subjects were evaluated by Turkish version of Minimental State Examination (MMSE), Clinical dementia rating (CDR) and Global deterioration scale (GDS).

Results: The mean age of patients and controls were 72.33±10.11 and 67.20±8.95, respectively. There was not any significant difference between age of the patients and the controls (p=0.054). Both patient and control groups consisted of mostly women (60% and 56% respectively). The mean waist circumferences (WC) of patients and controls were 95.46±10.87 and 97.76±10.07, respectively and was not statistically different (p=0.424). The mean serum leptin levels in patients and controls were 5.49± 4.06 ng/dL 5.71±4.45 ng/dL, respectively. Leptin levels were not stastistically different between patients and controls (p=0.84). The mean MMSE scores of AD patients and controls were 17±6.54 and 27.32±2.15, respectively and AD patients had significantly lower MMSE scores than the controls (p=0.000). The mean BMI of patients and controls were 25.72±3.98 and 27.92±3.08 respectively. The BMI of controls were higher than patients and there was statistically significant difference between two groups (p=0.029). In the patient group, there were no correlations between leptin levels and age (p=0.067), BMI (p=0.098), WC (p=0.113), MMSE (p=0.203), CDR (p=0.519) and GDS (p=0.587). Similarly in control group leptin levels were not correlated with BMI (p=0.718), WC (p=0.755) and MMSE (p=0.859).

Conclusion: In the present study, we could not find any relation between blood leptin levels and cognition in AD patients.